$\left(2a-1\right)\left(2a^2+a\right)-4a$

$\frac{tan\left(x\right)+cot\left(y\right)}{\frac{tan\left(x\right)}{tan\left(y\right)}}$

$\lim_{x\to0}\left(\frac{3x^3-5x}{2x^2+1}\right)$

$x^2y'=xy$

$\frac{d}{dx}\frac{1}{5}\:at\:\frac{3}{4}$

$6\left(5000-x\right)+8x\ge370$

$\frac{1}{2\sin10}-2\sin\left(70\right)$